System and method for securing the life-cycle of user domain rights objects

ABSTRACT

In a method for enabling support for backwards compatibility in a User Domain, in one of a Rights Issuer (RI) and a Local Rights Manager (LRM), a Rights Object Encryption Key (REK) and encrypted REK are received from an entity that generated a User Domain Authorization for the one of the RI and the LRM and the REK is used to generate a User Domain Rights Object (RO) that includes the User Domain Authorization and the encrypted REK.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/551,772 filed on Nov. 24, 2015 which is a divisional of U.S. patentapplication Ser. No. 12/477,104, filed Jun. 2, 2009 and entitled,“SYSTEM AND METHOD FOR SECURING THE LIFE-CYCLE OF USER DOMAIN RIGHTSOBJECTS,” which shares some common features with U.S. patent applicationSer. No. 11/697,342, filed Apr. 6, 2007 and entitled “SYSTEM, DEVICE ANDMETHOD FOR INTEROPERABILITY BETWEEN DIFFERENT DIGITAL RIGHTS MANAGEMENTSYSTEMS,” which issued on Oct. 11, 2011 as U.S. Pat. No. 8,037,541. Theentireties of these applications are incorporated herein by reference.

BACKGROUND

Digital content has gained wide acceptance in the public. Such contentincludes, but is not limited to: movies, videos, music, and the like.Consequently, many consumers and businesses employ various digital mediadevices or systems that enable the reception of such digital multimediacontent via several different communication channels (e.g., a wirelesslink, such as a satellite link, or a wired link, such as a cableconnection). Similarly, the communication channel may also be atelephony based connection, such as DSL and the like. Regardless of thetype of channel, the digital content and/or the distribution of thedigital content is typically secured using a conditional access (CA)mechanism and a digital rights management (DRM) mechanism (e.g.,encryption/decryption using keys).

Presently, specifications are being developed with respect to expandingthe ways that content and services can be distributed over wirelesscommunication networks. One such set of standards is being developed bythe Open Mobile Alliance (OMA). In the OMA DRM system, for example,digital content (e.g., a movie or song) is associated with a rightsobject (RO). The RO provides granting rights to a client device forviewing or otherwise consuming the digital content. The entity in theclient device that manages permissions and corresponding constraintsrelative to use of the digital content is commonly denoted as a DRMAgent. Nominally, a DRM Agent obtains an RO from a rights issuer (RI).DRM Agents conformant to the new OMA Secure Content Exchange (SCE)specifications (as well as to the legacy OMA DRM v2.x (i.e. OMA DRM v2.0or OMA DRM v2.1) system) are intended to have the opportunity toparticipate in Rights transfers with other such DRM Agents, and to takefull advantage of User Domains for which potentially multiple Rls and/orLocal Rights Managers (LRM) create Rights Objects (designated as UserDomain ROs). In the legacy OMA DRM v2.x system a domain is associatedwith and managed by a single Rights Issuer, which implies that each DRMAgent needs to register with each RI for which it wants to makesuccessful use of Domain ROs generated by that RI. User Domains areintended to overcome that deficiency for SCE-conformant DRM Agents,while providing backwards-compatible domain support for legacy DRMAgents. This requires a secure association of Rights Issuers and/orLocal Rights Managers with a Domain Enforcement Agent (DEA) thatoperates under oversight of a Domain Authority (DA), such thatSCE-conformant DRM Agents can become members of (i.e., join) a UserDomain that is managed by that DEA, be able to provide proof ofmembership in the User Domain, and be assured that a Rights Issuer orLocal Rights Manager from which they accept User Domain Rights Objectsis legitimately associated with that User Domain.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments are illustrated by way of example and not limited in thefollowing figure(s), in which like numerals indicate like elements, inwhich:

FIG. 1 illustrates a block diagram of a digital rights management (DRM)system operable in a secure content exchange (SCE) User Domain,according to an embodiment of the invention;

FIG. 2 depicts a block diagram of a Local Rights Manager (LRM),according to an embodiment of the invention;

FIG. 3 depicts a flow diagram of a method for enabling support forbackwards compatibility for legacy DRM Agents, according to anembodiment of the invention;

FIG. 4 depicts a flow diagram of a method for targeting a User Domain ROto a specific SCE-conformant DRM Agent, according to an embodiment ofthe invention;

FIG. 5 depicts a flow diagram of a method of moving a User Domain ROfrom a source SCE-conformant DRM Agent to a recipient SCE-conformant DRMAgent through operation of a Rights Issuer, according an embodiment ofthe invention;

FIG. 6 depicts a flow diagram of a method of directly moving a UserDomain RO from a source SCE-conformant DRM Agent to a recipientSCE-conformant DRM Agent, according to an embodiment of the invention;and

FIG. 7 shows a block diagram of a computing apparatus configured toimplement or execute one or more of the processes depicted in FIGS. 3-6.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the principles of theembodiments are described by referring mainly to examples thereof. Inthe following description, numerous specific details are set forth inorder to provide a thorough understanding of the embodiments. It will beapparent however, to one of ordinary skill in the art, that theembodiments may be practiced without limitation to these specificdetails. In other instances, well known methods and structures have notbeen described in detail so as not to unnecessarily obscure theembodiments.

DEFINITIONS

As used herein, the “domain authority” or “DA” entity is characterizedby certificate with a domainAuthority key purpose. In addition, the DAtype of entity is intended to be a service provider.

The “domain enforcement agent” or “DEA” entity is characterized bycertificate with domainEnforcementAgentNetwork ordomainEnforcementAgentLocal key purpose. ThedomainEnforcementAgentNetwork is typically a service provider. ThedomainEnforcementAgentLocal is typically a home-network entity, forinstance, within a set-top box (STB) or a mobile device.

The “rights issuer” or “RI” entity is characterized by certificate withrightsIssuer key purpose, without localRightsManagerDevice key purpose,and without localRightsManagerDomain Key purpose. This entity type istypically a service provider.

The “local rights manager” or “LRM” is characterized by certificate withlocal RightsManagerDevice key purpose and/or localRightsManagerDomainKey purpose; such certificate may additionally include rightsIssuer keypurpose. This entity type is typically a home-network entity (within anSTB or mobile device that has access to upstream non-OMA DRM content andto rights that may be imported into OMA DRM (enabling DRMinteroperability)). By way of example, the LRM (or associated softwareand/or hardware) is configured to convert signals to remove upstreamnon-OMA DRM protection on content, and in certain instances, to alsotranscode the content so that the resultant content matches thecharacteristics and/or limitations of the destination device. The LRM isconfigured to generate Rights Objects to enable cryptographic access toand controlled use of the OMA-DRM-protected content. By way of example,the LRM (or associated software and/or hardware) is configured topackage the (possibly transcoded) content in OMA-DRM protected contentform so that the resulting DRM Content Format (DCF), or Packetized DRMContent Format (PDCF) (for Continuous Media), can be made available toDRM Agents.

The “v2.x Device” entity is characterized by certificate with drmAgentkey purpose, and without sceDrmAgent key purpose. The v2.x Device entitymay comprise, for instance, a v2.0 or v2.1 device without SCE.

The “SCE Device” is characterized by certificate with drmAgent keypurpose and sceDrmAgent key purpose. The SCE Device may include, forinstance, a v2.1 DRM Agent. An SCE Device is distinguishable from a v2.xDevice by an SCE-conformant RI and by another SCE Device (based oninclusion of sceDrmAgent key purpose). The SCE Device certificate mustinclude drmAgent key purpose in order to be recognized by a v2.x RI. InOMA DRM v2.x, Devices do not communicate with each other using acryptographic protocol and thus do not verify each other's certificate.

The “v2.x Domain” is a domain that is managed either by an RI, or by anLRM with rightsIssuer key purpose. The OMA DRM v2.1 DRM Specificationmakes no explicit mention of a Local Rights Manager (LRM) or of SecureContent Exchange (SCE), but Appendix I. (entitled “Import”) makesreference to “import user equipment.” In accordance with OMA DRM v2.1such an import user equipment would have to be furnished with acertificate that is completely indistinguishable from a certificateprovisioned to an RI. However, the newer SCE enabler allows foridentifying a new entity (namely, an LRM) that is distinguishable froman RI by SCE-conformant Rls and by SCE-conformant DRM Agents/Devices(alternatively denoted as SCE Devices). A v2.x DRM Agent/Device cannotdifferentiate an LRM with rightsIssuer key purpose from an actual RI.Moreover, a v2.x Device may join a v2.x Domain and thus acquire(Domain-specific and Domain generation-specific) Domain key(s) via theRI, or via the LRM with rightsIssuer key purpose, while ignoring otherkey purposes, so that an LRM with rightsIssuer key purpose isessentially an RI from the perspective of the device. However, an SCEDevice may not join a v2.x Domain managed by an LRM.

The “User Domain” is a domain that is managed by a DEA under theoversight of a DA in the form of a digitally-signed User DomainAuthorization provided by the DA to the DEA for dissemination to relyingRls, LRMs, and SCE Devices. A v2.x Device may join a User Domain in thesame manner that the v2.x Device may join a v2.x Domain and may not beaware that the v2.x Device is joining a User Domain. That is, the v2.xDevice registers with an RI, or LRM with rightsIssuer key purpose, inorder to establish an RI Context in the v2.x Device, and joins the UserDomain (using the OMA DRM v2.x Join Domain Protocol), resulting in aDomain Context in the v2.x Device. Thus a v2.x Device may belong to anidentical User Domain through multiple instances, each with a distinctRI or LRM with rightsIssuer key purpose. After registering with a DEA(resulting in a DEA Context), an SCE Device may join a specific UserDomain managed by that DEA (resulting in a User Domain Context), andthus acquire (User Domain-specific and User Domain generation-specific)User Domain Key(s). This allows consolidation in that multiple RI(s)and/or LRM(s) may input to a single User Domain, thus enabling an SCEDevice that has no context with the RI or LRM that initially created theUser Domain Rights Object to consume based on its membership in the UserDomain via the managing DEA. An SCE Device, furthermore, may maintainseveral User Domain Contexts relative to a single DEA, eachcorresponding to a single User Domain managed by that DEA. An SCE Devicethat does have an RI Context or LRM Context with an RI or LRM,respectively, may request a User Domain Rights Object directly from thatentity without the need to join a domain using the OMA DRM v2.x JoinDomain Protocol with that entity. The registration protocol used by anSCE Device with a DEA is designated in the SCE DOM TechnicalSpecifications as the DRM Agent-DEA Registration Protocol, and theprotocol used by an SCE Device to join a User Domain is designated inthe SCE DOM Technical Specifications as the Join User Domain Protocol.As part of the DRM Agent-DEA Registration Protocol the SCE Device mayreceive a symmetric key (SK) and a message integrity key (MK) toestablish a Security Association (SA) enabling to secure theconfidentiality and integrity, respectively, of later communicationsbetween the SCE Device and the DEA, such as communications required forexecution of the Join User Domain Protocol. In order to establish a UserDomain Context, the SCE Device must have acquired a User DomainAuthorization signed by a Domain Authority (DA) that identifies theparticular DEA and the particular User Domain. If such User DomainAuthorization indicates the need for SCE Device-specific DA-signed UserDomain Authorizations, the SCE Device must also acquire such a UserDomain Authorization that identifies itself and the DEA. Successfulexecution of the Join User Domain Protocol results, in particular, inacquisition by the SCE Device of a User Domain Authorization signed bythe DEA that identifies the SCE Device and the particular User Domain.In addition, the SCE Device may receive one or more User DomainAuthorizations signed by the DEA such that each identifies a particularRI or LRM (as well as the particular User Domain).

The “Device Rights Object” is initially targeted by an RI or LRM to asingle specific Device. If the Device Rights Object is initiallyintended for a v2.x Device, the LRM's certificate must include arightsIssuer key purpose. If the device rights object is initiallyintended for an SCE Device, the LRM's certificate must include alocalRightsManagerDevice key purpose.

Although a v2.x Domain Rights Object is created by an RI or LRM withrightsIssuer key purpose by directly using the current generation of theappropriate Domain Key, this is not the case for the analogousgeneration of a User Domain Rights Object.

Referring first to FIG. 1, there is shown a block diagram of a digitalrights management (DRM) system 10 operable in a secure content exchange(SCE) User Domain, according to an embodiment of the invention. Itshould be understood that the following description of the DRM system 10is but one manner of a variety of different manners in which such a DRMsystem 10 may be configured and operated. In addition, it should beunderstood that the DRM system 10 may include additional components andthat some of the components described may be removed and/or modifiedwithout departing from a scope of the DRM system 10.

As shown in FIG. 1, the DRM system 10 includes a content source orprovider 12, an upstream digital rights issuer (RI) 14 associated withthe content provider 12, a network 16 coupled to the content provider 12and/or the upstream RI 14, and an upstream distribution system 18coupled to the network 16. The content provider 12, the upstream RI 14,the network 16 and the upstream distribution system 18 are part of anupstream system or an upstream DRM system, which, in general, is the DRMsystem or portion of the DRM system in which the content originates orfrom which the content is distributed.

The system 10 also includes a Local Rights Manager (LRM) 22 and a DomainEnforcement Agent (DEA) 24, both of which may be part of a downstreamdistribution system, shown generally as 26, which is coupled to theupstream distribution system 18. As will be discussed in greater detailhereinbelow, the LRM 22 is generally configured to translate upstreamlicenses and protected content and issues licenses and other digitalrights to one or more of the end user communication devices in thedownstream system. Translation is the process that takes upstreamlicenses and protected content and makes that information available inthe downstream DRM system. Thus, at least functionally, the LRM 22 alsomay be considered to be part of the upstream distribution system 18, orat least straddling the upstream and downstream systems. Also, as willbe discussed in greater detail hereinbelow, the DEA 24 defines andmanages the “User Domain,” which is the set of end user communicationdevices that are allowed to share Domain Licenses. End usercommunication devices in the same domain share a Domain key, as alsodiscussed in greater detail herein below.

The DRM system 10 also includes a network 28 that couples the downstreamdistribution system 26 to one or more end user communication devices 32,34 and 36. The downstream distribution system 26, the network 28 and theend user communication devices 32, 34, 36 are part of a downstreamsystem or downstream DRM system. In general, the downstream DRM systemis the DRM system or portion of the DRM system to which the protectedcontent is transmitted or distributed. As discussed, translation is theprocess that takes upstream licenses and protected content and makesthat information available in the downstream DRM system.

Also shown in FIG. 1 is a downstream RI 22, which may be provided in thedownstream distribution system 26, for instance, when the downstreamdistribution system 26 does not have an LRM, or may be provided inaddition to and independently of an LRM 22. In addition, the downstreamRI 22 may be associated with a downstream content provider (not shown)that differs from the upstream content provider 12.

The LRM/downstream RI 22 is provisioned with an identity certificate,which includes a public key corresponding to a private key that isprovisioned to the LRM/downstream RI 22, and an attributecertificate/authorization certificate, which identifies theLRM/downstream RI 22 as well as the particular User Domain. Theattribute certificate, which is often designated as a User DomainAuthorization, is signed by the DEA 24, which manages the User Domain.In addition, the User Domain Authorization does not include a public keyof the identified LRM/downstream RI 22. A device 32-36, may determinethat the LRM/downstream RI 22 is authorized to issue domain ROs for aparticular User Domain managed by a particular DEA 24 based upon theUser Domain Authorization of the LRM/downstream RI 22 that is signed bythe DEA 24. In addition, the DEA 24 may determine whether or not theLRM/downstream RI 22 is authorized to register with the DEA 24 and/ormay determine whether or not the LRM/downstream RI 22 is authorized tobe associated with a particular User Domain.

One means by which the DEA 24 may make a determination as to whether ornot the LRM/downstream RI 22 is authorized to be associated with aparticular User Domain is by attempting to procure a User DomainAuthorization that is signed by the DA 38 and that identifies the DEA 24and the particular LRM/downstream RI 22. The User Domain Authorizationthat is signed by the DA 38 and that identifies the DEA 24 and aparticular User Domain may include an element that indicates to the DEA24 and LRM/downstream RI 22 that a separate User Domain Authorizationthat is signed by the DA 38 and that identifies the DEA 24 and theparticular LRM/downstream RI 22 is required in order for theLRM/downstream RI 22 to be authorized to be associated with the UserDomain by that DEA 24. If such an element is present, it is necessaryfor the DEA 24 to procure a distinct such User Domain Authorization thatidentifies the LRM/downstream RI 22 for each LRM/downstream RI 22 theDEA 24 associates with the User Domain. It is not necessary for the DEA24 to procure a distinct such User Domain Authorization that identifiesthe LRM/downstream RI 22 for each User Domain.

The LRM 22 and/or a downstream RI 22 registers with the DEA 24. Thisprotocol is designated in the SCE DOM Technical Specifications as theRI-DEA Registration Protocol. A successful execution of the RI-DEARegistration Protocol results in a DEA Context in the downstream RI orLRM 22. As part of the RI-DEA Registration Protocol, the downstream RIor LRM 22 may receive a symmetric key (SK) and a message integrity key(MK) to establish a Security Association (SA) enabling to secure theconfidentiality and integrity, respectively, of later communicationsbetween the downstream RI or LRM 22 and the DEA 24, such ascommunications required for execution of the Get User DomainAuthorization Protocol discussed herein below. As part of the protocolthat associates the downstream RI or LRM 22 with a particular UserDomain, the downstream RI or LRM 22 receives a User Domain Authorization(signed by the DEA 24) that represents its association with the DEA 24and with the particular User Domain; the downstream RI or LRM 22 mayalso receive a User Domain Authorization (signed by the DA 38) thatrepresents its association with the DEA 24. This protocol is designatedin the SCE DOM Technical Specifications as the Get User DomainAuthorization Protocol.

Successful execution of the Get User Domain Authorization Protocolresults in establishment of a new or updated User Domain Context in thedownstream RI or LRM 22 for that specific User Domain. Successfulexecution of the Get User Domain Authorization Protocol requires, inparticular, that the downstream RI or LRM 22 receive (or already have) acurrently valid User Domain Authorization signed by the DA 38 thatidentifies the particular DEA 24 and particular User Domain. It ispossible for a DEA 24 (such as that provisioned with a certificate withdomainEnforcementAgentLocal key purpose) to be pre-provisioned with aUser Domain Authorization signed by a DA 38 that identifies the DEA 24and a User Domain and that does not indicate the need for further(downstream RI- or LRM 22-specific or DRM Agent-specific) DA-signed UserDomain Authorizations, so as to enable “out-of-the-box” use of the DEA24 without the need to communicate with a DA 38.

According to an embodiment, the LRM and/or the downstream RI 22 receiveskeying material (during execution of the Get User Domain AuthorizationProtocol) that enables the LRM and/or the downstream RI 22 to generateUser Domain ROs, but that does not enable derivation of the User DomainKeys themselves that the Devices 32-36 may use to cryptographicallyaccess the User Domain ROs. In this embodiment, the registration of theLRM 22 and/or the downstream RI with the DEA 24 (using the RI-DEARegistration Protocol that precedes initial execution of the Get UserDomain Authorization Protocol) may differ from a standard registrationof a Device 32 with a downstream RI 22. More particularly, the RI-DEARegistration Protocol may differ in that the downstream RI and/or theLRM 22 receives Security Association (SA) keys that are used during theGet User Domain Authorization Protocol. These SA keys may be protectedduring transmission by using encryption based on the certified publickey of the downstream RI or LRM 22. For security, these SA keys aretypically assigned different values than those transmitted from the DEA24 to a Device 32 during execution of the DRM Agent-DEA RegistrationProtocol.

The content source or provider 12 may be any suitable transmissionsource of DRM-protected content, including multimedia content. Forexample, the content provider 12 may be an over-the-air broadcaster,from a cable television plant, satellite service provider or othercontent service provider, such as a telephone system. The contentprovider 12 may be connected to the network 16 and/or the upstreamdistribution system 18 via any suitable connection, e.g., one or morecoaxial cables and/or optical fibers or optical fiber cables, includinga Hybrid Fiber Coaxial (HFC) cable system. Other suitable connectionsinclude suitable Fiber To The Premises (FTTP) systems, such as Fiber ToThe Curb (FTTC) or Fiber To The Home (FTTH), or over any suitable numberof digital subscriber line systems (xDSL). Also, the content provider 12may provide DRM-protected content wirelessly, e.g., viaover-the-air-broadcast from a satellite service provider or othersuitable content service provider.

The content provided by the content provider 12 can be any multimediacontent, including DRM-protected content, that is suitable fortransmission to one or more end user communication devices. For example,multimedia content may include broadcast video, including movies,programming events, music and/or other multimedia content that isdistributed, e.g., as one or more programming streams from the contentprovider 12 or other suitable content source. The multimedia contenttypically is a plurality of digital signals formatted according to asuitable standard, such as the MPEG (Moving Picture Experts Group) 2 orMPEG 4 standard, and multiplexed into a data stream that is modulated ona carrier using quadrature amplitude modulation (QAM) or other suitablemodulation technique.

The upstream digital rights issuer 14 may be any suitable entityassociated with or system component, element and/or portion of thecontent provider 12 that is suitable for generating and/or providingcontent protection information associated with content provided by thecontent provider 12. In general, content protection information includeslicenses and any other digital rights issuance information that enablesthe use of associated content under specified conditions. For example,content protection information may include privileges, permissionsand/or constraints regarding access to its associated content by one ormore end user communication devices in the upstream distribution system18. A downstream RI 22 is associated with a content provider (not shown)that may be distinct from content provider 12. A downstream RI 22 issuitable for generating and/or providing content protection informationassociated with content provided by a content provider with which thedownstream RI is associated. Specific content protection informationwill be discussed hereinbelow.

One or more of the network 16, the upstream distribution system 18, thedownstream distribution system 26 and the network 28 may be anycommunication network or network server arrangement suitable fortransmitting DRM-protected content and associated rights issuanceinformation between the content provider 12 (and upstream RI 14) and oneor more of the end user communication devices in the upstreamdistribution system 18. For example, one or more of the network 16, theupstream distribution system 18, the downstream distribution system 26and the network 28 may be or include a cable television network, theInternet or an Internet protocol (IP) based or other packet-basednetwork, or other suitable public network, including a telephonenetwork. Also, one or more of the network 16, the upstream distributionsystem 18, the downstream distribution system 26 and the network 28 maybe or include a computer network, a web-based network or other suitablewired or wireless network or network system. Thus, one or moreconnections between any one or more of the network 16, the upstreamdistribution system 18, the downstream distribution system 26 and thenetwork 28 can be or include one or more coaxial cables and/or opticalfibers, including a Hybrid Fiber Coaxial (HFC) cable system, one or moreFiber To The Premises (FTTP) systems, such as Fiber To The Curb (FTTC)or Fiber To The Home (FTTH), over any suitable number of digitalsubscriber line systems (xDSL), and/or wirelessly.

One or more of the end user communication devices in the upstreamdistribution system 18 and one or more of the (downstream) end usercommunication devices 32, 34, 36 may be any suitable end usercommunication device configured to receive, process, store, displayand/or otherwise execute or consume DRM-protected content and/orassociated rights issuance information. For example, one or more of theend user communication devices can be any signal converter or decoder(set-top) box, including set-top boxes with internal and/or externalrecording capabilities and local and/or remote storage, which often arereferred to as personal video recorder (PVR) devices, digital videorecorder (DVR) devices and/or digital video server (DVS) devices. Othersuitable end user communication devices include residential gateways,home media server systems, digital video disk recorders, computers,televisions with built-in or added-on content receiving and storingcapability, and/or other suitable computing devices or content devices,including internet protocol (IP), satellite and cable digital videorecorders, and home area network (HAN) devices and systems. Also, one ormore of the end user communication devices can be mobile communicationdevices, such as cellular telephones, smart telephones (smartphones),personal digital assistants (PDAs), digital music players (e.g., MP3players), portable video players and/or other handheld mobile devices,media players in automobiles, laptop personal computers (PCs), notebookPCs and/or other mobile computing devices. The LRM 22 may be part of aset-top box (not shown) in the upstream distribution system 18.

Each of the end user communication devices 32, 34, 36 typically includesa DRM Agent (not shown), which is configured to obtain, e.g., from theLRM and/or a downstream RI 22, downstream content licenses and/or otherrights issuance information for items of content. The DRM Agent alsomanages the authentication/verification of the downstream contentlicense for a content item, the conditional access of the content item(e.g., decryption), and the enforcement of the DRM permissions specifiedin the downstream content license.

The DRM Agents of the communication devices 32-36 may be one of a v2.x(legacy) DRM Agent or an SCE-conformant DRM Agent. A device having av2.x DRM Agent may generally be considered as conforming to v2.0 or v2.1of the OMA DRM Specifications. A device having an SCE-conformant DRMAgent may generally be considered as conforming with the OMA SecureContent Exchange Specifications. A device having an SCE-conformant DRMAgent may generally be considered as additionally conforming to v2.1 ofthe OMA DRM Specifications. In this regard, in a v2.x Domain, the v2.xDRM Agent is managed by a downstream RI or by an LRM 22 withrightsIssuer key purpose. The provisioning of a certificate withrightsIssuer key purpose may be restricted to an LRM 22 that has thecapability to generate all the appropriate keys for issuing ROs, such asDomain Keys for v2.x Domain ROs. In addition, a v2.x DRM Agent may joina v2.x Domain, and thus acquire Domain Key(s) for the v2.x Domain from adownstream RI or the LRM 22 with rightsIssuer key purpose. However, anSCE-conformant DRM Agent is not able to join a v2.x Domain managed by anLRM 22.

In an SCE-Compliant Domain, e.g., a User Domain, a v2.x DRM Agent isable to join the User Domain as previously discussed with respect to thev2.x Domain. An SCE-conformant DRM Agent may join the User Domain, andthus acquire User Domain Key(s) via the DEA 24 that manages that UserDomain. In one regard, this allows consolidation in that multipledownstream RI(s) and/or LRM(s) may input to a User Domain, thus enablingan SCE-conformant DRM Agent that has no context with the downstream RIor LRM 22 that initially created the User Domain RO to consume based onits membership in the User Domain via the managing DEA 24.

A Device RO, as differentiated from a User Domain RO or v2.x Domain RO,is initially targeted by a downstream RI or LRM 22 to a single specificv2.x or SCE-conformant DRM Agent. If the Device RO was initiallyintended for a v2.x DRM Agent, the LRM's 22 certificate must include arightsIssuer key purpose. If the Device RO was initially intended for anSCE-conformant DRM Agent, the LRM's 22 certificate must include a localRightsManagerDevice key purpose.

A Domain RO or User Domain RO that is not further targeted (as discussedhereinbelow) differs from the Device RO in that the Domain RO or UserDomain RO is not initially intended for a particular device, butinstead, is intended for a particular v2.x Domain or User Domain. A DRMAgent is only able to access the Domain RO by going to the downstream RIto join the v2.x Domain. However, in a User Domain, an SCE-conformantDRM Agent need not go to the downstream RI that created the particularUser Domain RO, but instead, goes to the DEA 24.

Referring now to FIG. 2, with continuing reference to FIG. 1, shown is ablock diagram of the LRM 22/RI 22 used in the DRM system 10. The LRM/RI22 may be partially or completely any suitable device or subsystem (orportion thereof) within the downstream distribution system 26 and/or thenetwork 28 coupled thereto. In general, the LRM 22 is responsible forreceiving licenses and other digital rights issuance information fromthe upstream RI 14 and/or other components in the upstream portion ofthe DRM system 10 and controlling the issuance of those licenses anddigital rights to one or more end user communication devices 32-36.

The LRM 22 includes a processor or controller 42, an upstream DRM agent44 coupled to the processor 42, a translator 46 coupled to the processor42, and a content storage element 48 coupled to the processor 42. Ingeneral, the processor 42 processes content and associated DRMinformation received by the LRM 22. In addition to the content storageelement 48, the processor 42 may include at least one type of memory ormemory unit (not shown) and a storage unit or data storage unit coupledto the processor for storing processing instructions and/or informationreceived by the LRM 22.

The upstream DRM agent 44 is configured to receive content licenses andother digital rights issuance information from the upstream distributionsystem 18 for associated content. As discussed generally hereinabove,the upstream DRM agent 44 manages the authentication or verification ofthe content license for a content item, the conditional access of thecontent item (e.g., decryption), and the enforcement of the DRMpermissions and/or constraints specified in the content license. Suchinformation can be characterized as DRM data or DRM information.

The translator 46 converts or generates a converted version of thelicenses and/or other digital rights issuance information from a firstDRM format or scheme to at least one second DRM format or scheme. Forexample, the translator 46 translates DRM information issued accordingto the DRM format used by the upstream RI 14 to the DRM format supportedby the particular end user communication device to which the DRMinformation is being transferred, at least to the extent that such DRMformats or schemes are different and/or incompatible.

The LRM 22 also may include one or more input and/or output interfacesfor receiving and/or transmitting content and associated DRMinformation. For example, the processor 42 and other components in theLRM 22 may be coupled between a first or input interface 52, whichreceives content and associated DRM information from the upstreamdistribution system 18, and one or more second or output interfaces 56,which transfer processed content and associated DRM information,including stored content and associated DRM information, to one or moreend user communication devices. One or more input and output interfaces54 is coupled to the processor 42. It should be understood that one ormore of the interfaces 52, 54, 56 may be a single input/output interfacecoupled to the processor 42. Also, it should be understood that one ormore of the interfaces 52, 54, 56 may be an interface configured tosupport more than one upstream RI 14 and/or end user communicationdevice.

One or more of the processor 42, the upstream DRM agent 44, thetranslator 46, the content storage element 48 and the interfaces 52, 54,56 may be comprised partially or completely of any suitable structure orarrangement, e.g., one or more integrated circuits. Also, it should beunderstood that the LRM 22 includes other components, hardware andsoftware (not shown) that are used for the operation of other featuresand functions of the LRM 22 not specifically described herein.

The LRM 22 may be partially or completely configured in the form ofhardware circuitry and/or other hardware components within a largerdevice or group of components. Alternatively, the LRM 22 may bepartially or completely configured in the form of software, e.g., asprocessing instructions and/or one or more sets of logic or computercode. In such configuration, the logic or processing instructionstypically are stored in a data storage device, e.g., the content storageelement 48 or other suitable data storage device (not shown). The datastorage device typically is coupled to a processor or controller, e.g.,the processor 42. The processor 42 accesses the necessary instructionsfrom the data storage device and executes the instructions or transfersthe instructions to the appropriate location within the LRM 22.

With respect to the content storage element 48, the LRM 22 may haveaccess to a hard drive or other storage element for recording streams ofmultimedia content, such as video streams broadcast from the multimediacontent source. However, the content storage element 48 may be anysuitable information storage unit, such as any suitable magnetic storageor optical storage device, including magnetic disk drives, magneticdisks, optical drives, optical disks, and memory devices, includingrandom access memory (RAM) devices and flash memory. Also, although thecontent storage element 48 is shown within the LRM 22, the contentstorage element 48 can be located external to the LRM 22 and suitablycoupled thereto.

If a downstream RI 22 or LRM 22, where the LRM 22 has a certificate withrightsIssuer key purpose, created a v2.x Domain Rights Object (RO) atthe request of a particular v2.x DRM Agent, the v2.x DRM Agent may stillgo to that downstream RI or LRM 22 to make use of that RO by joining thev2.x Domain if not already a member or if the Domain has been upgraded,in order to receive the Domain Key (or perhaps multiple Domain Keys ifpast Domain Keys cannot be algorithmically derived by the v2.x DRM Agentfrom the current generation Domain Key). The same is true for anSCE-conformant DRM Agent in the case of a downstream RI 22, but not inthe case of an LRM 22, whether or not such LRM 22 has a certificate withrightsIssuer key purpose.

However, in a User Domain, the User Domain ROs are going to beattributable to a particular LRM/downstream RI 22 that produced the UserDomain ROs; whereas, the User Domain is managed by the DEA 24 ratherthan the LRM/downstream RI 22. So an SCE Device that seeks to make useof a User Domain RO is typically required to go to the DEA 24 toregister and join the User Domain. The downstream RI 22 and/or the LRM22 are also typically required to go to the DEA 24 to become associatedwith the User Domain. However, according to an embodiment of theinvention, the LRM/downstream RI 22 does not receive the User Domain Keyfrom the DEA 24 but is able to generate the User Domain ROs as discussedin greater detail herein below.

Although an SCE-conformant DRM Agent is able to join the User Domainbecause it is already registered with the DEA 24, and thus receives aUser Domain Key in order to make use of the User Domain RO, a v2.x DRMAgent may not possess an appropriate certificate of its own (such as onethat includes an sceDrmAgent key purpose) and/or may not be equipped torecognize the certificate of the DEA 24 (such as the presence of adomain EnforcementAgentNetwork or domainEnforcementAgentLocal keypurpose), so as to register with the DEA 24 or to join the User Domainvia the DEA 24, and thus may be unable to make use of the User Domain ROby this means. Thus, a v2.x DRM Agent may join a User Domain by the sameprocess as joining a v2.x Domain in so far as the process is visible tothe v2.x DRM Agent. The v2.x DRM Agent remains oblivious to anyinteraction between the LRM 22 with (at least) rightsIssuer key purposeand local RightsManagerDomain key purpose or the downstream RI 22 andthe DEA 24.

In addition, a User Domain Key may not be delivered the first time to aparticular v2.x DRM Agent without the express permission and involvementof the DEA 24 because rather than receiving a v2.x Domain Key derivedfrom the User Domain Key from the DEA 24, each upstream RI 14 andLRM/downstream RI 22 associated with the User Domain receivesalternative keying material from the User Domain Key, in which thisalternative keying material cryptographically enables the generation ofUser Domain Rights Objects, but does not enable unilateral joining of av2.x DRM Agent to the User Domain by a downstream RI 22 or LRM 22 withrightsIssuer key purpose without the involvement of the DEA 24 at leastthe first time that v2.x DRM Agent attempts to join the currentgeneration of the User Domain. The alternative keying material is in theform of a Rights Object Encryption Key (REK) and message authentication(MAC) keys, where one such MAC key may be used by the downstream RI 22or LRM 22 to trigger a v2.x DRM Agent to leave the instance of the UserDomain relative to that particular LRM/downstream RI 22. In addition,the DEA 24 may encrypt the REK and the MAC keys under the appropriateUser Domain Key prior to communicating the REK and MAC keys to theLRM/downstream RI 22, since the LRM/downstream RI 22 is incapable ofdoing that due to lack of knowledge of the User Domain Key.

Moreover, all or part of the following may be transmitted as part of theexecution of the Get User Domain Authorization Protocol, possibly in aform encrypted for confidentiality using SK and integrity-protectedusing MK based on a Security Association (SA) that may have been set upas a result of having executed the RI-DEA Registration Protocol: K_(MAC)(i.e., a MAC key used by the LRM/downstream RI 22 when generating a UserDomain RO), K_(REK) (i.e., a REK used by the LRM/downstream RI 22 whengenerating a User Domain RO), AES-WRAP (UDK, K_(MAC)|K_(REK)) (i.e., theAES-WRAP encryption, using the User Domain Key (UDK), of theconcatenation of K_(MAC) and K_(REK), that is used by the LRM/downstreamRI 22 when generating a User Domain RO, K_(MAC)-Leave (i.e., a MAC keyused by the LRM/downstream RI 22 when a v2.x DRM Agent is triggered toleave the User Domain), and AES-WRAP (UDK, K_(MAC-Leave)) (i.e., theAES-WRAP, using the UDK, of K_(MAC-Leave) that is used by theLRM/downstream RI 22 when a Device is triggered to leave the UserDomain.

Some of the operations performed by and interactions between theLRM/downstream RI 22, and the DEA 24 are described in greater detailwith respect to the method 100 depicted in FIG. 3. FIG. 3, moreparticularly, depicts a flow diagram of a method 100 of enabling supportfor backwards compatibility for legacy DRM Agents in a User Domain,according to an embodiment of the invention. It should be understoodthat the method 100 depicted in FIG. 3 may include additional steps andthat some of the steps described herein may be removed and/or modifiedwithout departing from a scope of the method 100.

At step 102, the LRM/downstream RI 22 is registered with the DEA 24 as aprerequisite to becoming associated with the User Domain or one of theUser Domains that is managed by the DEA 24. As part of the get UserDomain Authorization process, at step 104, the DEA 24 generates a UserDomain Authorization for the LRM/downstream RI 22 that identifies theLRM/downstream RI 22 and the particular User Domain, and that is signedby the DEA 24. Additionally, as part of the get User DomainAuthorization process, the DEA 24 generates a key set comprised ofK_(MAC), K_(REK), AES-WRAP (UDK, K_(MAC)|K_(REK)) (i.e., the AES-WRAPencryption, using the User Domain Key (UDK), K_(MAC-Leave), andAES-WRAP(UDK, K_(MAC-Leave)). As described hereinabove, one or more ofthe elements of this key set may be encrypted using the SecurityAssociation (SA) that was established as part of the registration of theLRM/downstream RI 22 with the DEA 24 at step 102. The entire message maybe integrity protected using this SA.

The message may also include one or more DA-signed User DomainAuthorizations, such as identifying the DEA 24 and the User Domain,and/or identifying the DEA 24 and the particular LRM/downstream RI 22,as described hereinabove. As described herein above, K_(MAC-Leave), andAES-WRAP(UDK, K_(MAC-Leave)) are intended to be used by an RI 22 or anLRM 22 with certificate that includes rightsIssuer key purpose (as wellas localRightsManagerDomain key purpose), and thus need not betransmitted by the DEA 24 to an LRM 22 that has localRightsManagerDomain key purpose (and possibly localRightsManagerDevicekey purpose) but not rightsIssuer key purpose.

At step 106, the LRM/downstream RI 22 receives the message generated atstep 104. In particular the LRM/downstream RI 22 receives the (possiblySA-based encrypted and integrity-protected) Rights Object Encryption Key(REK) and encrypted REK from an entity that generated a User DomainAuthorization for the LRM/downstream RI 22. By virtue of the encryptionaspect of the first wrapping and the second wrapping under the UserDomain Key, the LRM/downstream RI 22 receives matched plain andciphertext rather than the key that allows a conversion from the plaintext to ciphertext. In addition, instead of communicating the key, whichin this case is the UDK, so that the LRM/downstream RI 22 may go fromplain text to ciphertext, the DEA 24, at step 106, is communicatingmatched plain text and ciphertext to the LRM/downstream RI 22. TheLRM/downstream RI 22 is able to use the matched plan text and theciphertext to create the User Domain ROs.

At step 108, the LRM/downstream RI 22 uses the REK to generate a UserDomain Rights Object (RO) that includes the User Domain Authorizationand the encrypted REK. More particularly, the User Domain RO iscryptographically accessible to any v2.x (legacy) DRM Agent that haspreviously been registered with the particular LRM 22 with, inparticular, rightsIssuer key purpose or with the particular downstreamRI 22, and has an RI/LRM-specific and domain-specific-domain context.The legacy DRM Agent may be registered with the particularLRM/downstream RI 22 in manners similar to those as prerequisite forjoining legacy Domains. The communications between the legacy DRM Agentand the LRM/downstream RI 22 to enable joining a User Domain may be donein manners similar to those used for joining legacy Domains. The UserDomain RO is also cryptographically accessible to any SCE-conformant DRMAgent that possesses knowledge of the User Domain Key for theappropriate generation of the User Domain.

According to an embodiment, at step 108, the LRM/downstream RI 22generates the User Domain ROs (or User Domain Constrained ROs describedhereinbelow) without making use of a User Domain Key, either on thedownstream side or the upstream side. Instead, the LRM/downstream RI 22overlays the so-called RO acquisition protocol with the User DomainAuthorization, regardless of whether the Device has a v2.x DRM Agent oran SCE-conformant DRM Agent. More particularly, a backwards-compatibleUser Domain RO may be generated for use by v2.x DRM Agents orSCE-conformant DRM Agents, by using the REK provided by the DEA 24 andincluding the encrypted REK in the RO, whereas a User Domain ConstrainedRO initially targeted to a particular SCE-conformant DRM Agent may begenerated by using an REK chosen by the LRM/downstream RI 22. As will bediscussed herein below, in the case of a User Domain Constrained RO theUser Domain Authorization overlay includes acquisition by theLRM/downstream RI of a DEA-signed User Domain Authorization thatidentifies the particular SCE-conformant DRM Agent and the User Domainas a condition of the LRM/downstream RI generating the User DomainConstrained RO targeted to that SCE-conformant DRM Agent. In both thecase of the backwards-compatible User Domain RO and User DomainConstrained RO, a DEA-signed User Domain Authorization that identifiesthe particular LRM/downstream RI and the User Domain may be included aspart of the RO, although a v2.x DRM Agent may ignore the embedded UserDomain Authorization.

At step 110, the LRM/downstream RI 22 communicates the User DomainConstrained RO with the User Domain Authorization overlay to a Device3236 with an SCE-conformant DRM Agent, or the LRM/downstream RI 22distributes the backwards-compatible User Domain RO using the so-calledRO acquisition protocol, or in a potentially out-of-band manner since itis intended to be usable by any v2.x DRM Agent or SCE-conformant DRMAgent that has become a member of the User Domain via that particularLRM/downstream RI 22 or via the DEA 24, respectively. The SCE-conformantDRM Agents are able to make use of the User Domain Constrained ROsthrough application of techniques that are similar to the legacy mannerof handling Device ROs. The v2.x DRM Agents are able to make use of thebackwards-compatible User Domain ROs through application of techniquesthat are similar to the legacy manner of handling Domain ROs. In eithercase, the LRM/downstream RI 22 provides the User Domain ROs (or UserDomain Constrained ROs) without making use of a User Domain Key.

When a v2.x DRM Agent receives the backwards-compatible User Domain ROoverlaid with the User Domain Authorization, the v2.x DRM Agent ignoresthe User Domain Authorization, and may join the User Domain in thestandard manner of joining a v2.x Domain when processing a Domain ROthat corresponds to a Domain of which the v2.x DRM Agent is not yet amember, such as by contacting an RI based on the RI URL in the relevantDCF. When an SCE-conformant DRM Agent receives the backwards-compatibleUser Domain RO overlaid with the User Domain Authorization, theSCE-conformant DRM Agent may join the User Domain, if not already amember, by determining from the User Domain Authorization the UserDomain ID and the identity and contact URL of the DEA responsible forthe particular User Domain.

Joining the User Domain enables a v2.x DRM Agent or SCE-conformant DRMAgent to make use of backwards-compatible User Domain ROs. As such, theLRM/downstream RI 22 does not need to have access to the User Domain Keyfrom the DEA 24 in order to generate User Domain ROs that are compatibleto both v2.x and SCE-conformant DRM Agents. As a condition of generatinga User Domain Constrained RO, the LRM/downstream RI 22 may verify thatthe intended recipient SCE-conformant DRM Agent is already a currentmember of the User Domain, based on a DEA-signed User DomainAuthorization that identifies the particular SCE-conformant DRM Agentand the User Domain.

In one regard, by not granting access to the User Domain Key or anyderived Domain Key to the LRM/downstream RI 22, the User Domain Key isnot corrupted due to an LRM/downstream RI 22 going bad or otherwisebecoming rogue. In another regard, the LRM/downstream RI 22 may continueto reuse the REK and MAC key (K_(MAC)) for each User Domain RO until theUser Domain is upgraded. As such, the bandwidth requirements between theupstream RI 14 and/or the LRM/downstream RI 22 and the DEA 24/DA 38 maybe relatively low.

According to an embodiment, the DA 38 may be enabled to turn on or offthe permission for a DEA 24 to participate in joining a v2.x DRM Agentto a particular User Domain by including such indication in theDA-signed User Domain Authorization that identifies the DEA and the UserDomain. In another embodiment, an LRM/downstream RI 22 may be alerted toas to whether or not the LRM/downstream RI 22 is allowed to participatein joining a v2.x DRM Agent to a particular User Domain by includingsuch indication in the DEA-signed User Domain Authorization thatidentifies the particular LRM/downstream RI 22 and the User Domain.

With reference now to FIG. 4, there is shown a flow diagram of a method200 for targeting a User Domain RO to a specific SCE-conformant DRMAgent, according to an embodiment of the invention. It should beunderstood that the method 200 depicted in FIG. 4 may include additionalsteps and that some of the steps described herein may be removed and/ormodified without departing from a scope of the method 200.

Generally speaking, the downstream RI 22 and/or the LRM 22 with acertificate with, in particular, localRightsManagerDomain key purpose,is configured to target a User Domain RO to a particular SCE-conformantDRM Agent without making use of a User Domain Key (where such a targetedUser Domain RO is referred to as a <userDomain>-constrained RO withinthe OMA SCE Technical Specifications to differentiate it from abackwards-compatible User Domain RO). As such, and as discussed above,the LRM/downstream RI 22 may not be provided with a User Domain Key forthe User Domain, which affords certain security benefits. Instead, theLRM/downstream RI 22 is configured to use a User Domain Authorizationfrom the SCE-conformant DRM Agent as assurance that it is acceptable togenerate the User Domain RO for use by that particular DRM Agent becausethe DRM Agent has indirectly proven its knowledge of the User DomainKey. Unlike the case of a backwards-compatible User Domain RO, the DRMAgent does not explicitly use knowledge of the User Domain Key in orderto enable recovery of the REK. Prior to using the targeted User DomainRO to access the associated content, the SCE-conformant DRM Agent maydetermine that the LRM/downstream RI 22 is authorized to deliver theUser Domain RO, by verifying the User Domain Authorization of theLRM/downstream RI 22, where such User Domain Authorization may be partof the User Domain RO and/or delivered separately from the User DomainRO.

Alternatively to receiving a User Domain Authorization for theSCE-conformant DRM Agent from the SCE-conformant DRM Agent, theLRM/downstream RI 22 may receive the User Domain Authorization of theSCE-conformant DRM Agent from the DEA 24. This User Domain Authorizationcould be received by other alternative means since its confidentialityneed not be protected in transit and its source and validity isverifiable because the User Domain Authorization has been signed by theDEA 24 and identifies the particular SCE-conformant DRM Agent and theUser Domain. The identification of the User Domain may include, inparticular, an indication of the specific generation of the User Domain.Similarly, the User Domain Authorization of the LRM/downstream RI 22 issigned by the DEA 24 and identifies the particular LRM/downstream RI 22and the User Domain. The LRM/Downstream RI 22 may have previously storeda still valid User Domain Authorization for the Device and thus notrequire receipt of a new one. At the point of requesting a User DomainRO, the SCE-conformant DRM Agent need not be aware of whether suchrequest will result in a backwards-compatible User Domain RO or atargeted User Domain RO. If the LRM/downstream RI 22 intends to issue atargeted User Domain RO but does not have a properly formatted currentlyvalid User Domain Authorization for the SCE-conformant DRM Agent readilyavailable, it may indicate within its response that an RO cannot beissued until such situation is rectified. The presence of a top-level<userDomain> constraint in a targeted User Domain RO may serve toindicate to a v2.x DRM Agent that the User Domain RO is not meant forits use.

Initially, and as indicated at step 202, the SCE-conformant DRM Agent isvalidated to, for instance, prove that the SCE-conformant DRM Agent hasproperly joined the User Domain. More particularly, for instance, whenthe SCE-conformant DRM Agent joined the User Domain, the SCE-conformantDRM Agent received an attribute certificate from the DEA 24 in the formof a User Domain Authorization as described herein immediately above. Inaddition, during the User Domain RO request process, the SCE-conformantDRM Agent communicates the attribute certificate to the LRM/downstreamRI 22 and the LRM/downstream RI 22 stores that attribute certificate. Atstep 202, the SCE-conformant DRM Agent essentially proves to theLRM/downstream RI 22 delivering the User Domain RO that theSCE-conformant Agent is in the User Domain. The SCE-conformant DRM Agentmay request a User Domain RO without including a User DomainAuthorization. In addition, the LRM/Downstream RI 22 does not require aUser Domain Authorization of the DRM Agent if the RO is generated as abackwards-compatible User Domain RO. Moreover, the LRM/downstream RI 22may generate a targeted User Domain RO without an explicit request fromthe SCE-conformant DRM Agent. Furthermore, the LRM/Downstream RI 22 maydetermine the SCE-conformant aspect of the DRM Agent by means ofverifying that the certificate of the DRM Agent includes an sceDrmAgentkey purpose (as well as a drmAgent key purpose).

The LRM/downstream RI 22 may also be able to determine that theSCE-conformant DRM Agent is in the User Domain if the LRM/downstream RI22 previously responded to a User Domain RO request from theSCE-conformant DRM Agent that included a valid User Domain Authorizationfor the DRM Agent. Such request may have resulted in generation by theLRM/downstream RI 22 of a targeted User Domain RO communicated to thatDRM Agent. Such request may have alternatively resulted in generation bythe LRM/downstream RI 22 of a backwards-compatible User Domain ROcommunicated directly or in an out-of-band manner to the DRM Agent.However, if a relationship between the LRM/downstream RI 22 and the DRMAgent was not formed, the SCE-conformant DRM Agent must prove to theLRM/downstream RI 22 that it has a current User Domain Authorization. Ifthe SCE-conformant DRM Agent does not have a current User DomainAuthorization, the LRM/downstream RI 22 will reject a request for the ROfrom that DRM Agent unless the LRM/downstream RI 22 generates abackwards-compatible User Domain RO. A request for abackwards-compatible User Domain RO does not require a User DomainAuthorization corresponding to the requesting DRM Agent and may be madeby a v2.x DRM Agent or an SCE-conformant DRM Agent. Abackwards-compatible User Domain RO may be generated and safely releasedbecause it cannot be cryptographically accessed without knowledge of theUDK.

At step 206, the LRM/downstream RI 22 generates a targeted User DomainRO for the SCE-conformant DRM Agent without using a User Domain Key.Instead, the LRM/downstream RI 22 generates the targeted User Domain RObased upon mutual attribute certificates, which are also called UserDomain Authorizations. The LRM/downstream RI 22 may store and reuse theUser Domain Authorizations as needed for the targeted User Domain ROs.Although the LRM/downstream RI 22 may receive the REK and encrypted REKinformation from the DEA 24 and may use the REK to generatebackwards-compatible User Domain ROs as discussed above with respect tosteps 106 and 108 in FIG. 3, this process is not used for generation oftargeted (i.e. <userDomain>-constrained) User Domain ROs.

Instead, the process of requesting and receiving User Domain ROs isbased on the standard RO acquisition protocol together with an overlayof User Domain Authorizations, where the construction of abackwards-compatible User Domain RO is similar to the construction of av2.x Domain RO (and appears to be a v2.x Domain RO to a v2.x Device ifgenerated by an RI 22 or an LRM 22 with rightsIssuer key purpose)whereas the construction of a targeted User Domain RO is similar to theconstruction of a v2.x Device RO. The encryption of the REK in a DeviceRO or in a targeted User Domain RO is based on use of the targeted DRMAgent's certified public key rather than on use of a Domain Key or UDK.In a backwards-compatible User Domain RO, according to an embodiment,there is no explicit use made of a UDK by the downstream RI/LRM 22 thatdoes not have knowledge of the UDK. However, there is implicit usebecause the (AES-Wrap) encryption of REK (concatenated with K_(MAC))under the UDK is incorporated into the RO. To cryptographically access abackwards-compatible User Domain RO, a v2.x DRM Agent or SCE-conformantDRM Agent uses its knowledge of UDK, whereas to cryptographically accessa targeted User Domain RO, the SCE-conformant DRM Agent uses itsknowledge of its own private key that corresponds to its certifiedpublic key.

Generally speaking, the targeted User Domain RO generated by theLRM/downstream RI 22 is similar to a Device RO. One result of thissimilarity is that the target SCE-conformant DRM Agent will be unable tomove the User Domain RO outside of the User Domain. Instead, the UserDomain RO will only be allowed to move within the User Domain becausethe User Domain RO is associated with a User Domain that is locked in bythe LRM/downstream RI 22 under this signature.

In any regard, at step 208, the LRM/downstream RI 22 that generated thetargeted User Domain RO communicates the targeted User Domain RO to theSCE-conformant DRM Agent.

As discussed above, the LRM/downstream RI 22 may generate a targetedUser Domain RO for a specific SCE-conformant DRM Agent. In variousinstances, the targeted User Domain RO may be “moved” from a sourceSCE-conformant DRM Agent, which may comprise the initially targetedSCE-conformant DRM Agent, to a sink SCE-conformant DRM Agent. Accordingto an embodiment, a downstream RI 22 may perform the move from thesource SCE-conformant DRM Agent to the sink SCE-conformant DRM Agent.This RI-assisted move may be done in an asynchronous fashion, in that,as part of the request by the source SCE-conformant DRM Agent to the RI22, the source SCE-conformant DRM Agent may identify the intended sinkSCE-conformant DRM Agent (or leave that determination to the assistingRI), but following receipt of the response from the RI, the sourceSCE-conformant DRM Agent is no longer involved. Based on the responsefrom the RI, the source SCE-conformant DRM Agent may determine whetheror not it can continue to use the rights, i.e., whether or not the RIintends to deliver a targeted User Domain RO corresponding to thoserights to a sink SCE-conformant DRM Agent. The source SCE-conformant DRMAgent may kill the rights for which it requested a move corresponding tothe User Domain RO stored thereon if the response from the RI 22indicated success.

The sink or recipient SCE-conformant DRM Agent may be triggered by theRI to request the targeted User Domain RO that the RI generated based atleast in part on the information supplied by the source SCE-conformantDRM Agent. Within the RO acquisition protocol response, the RI 22 mayindicate to the sink or recipient SCE-conformant DRM Agent that the UserDomain RO in the response is a targeted User Domain RO resulting from amove requested by a source SCE-conformant DRM Agent (without necessarilyidentifying the source SCE-conformant DRM Agent). This indicates to thesink DRM Agent that the RO is to be processed as a targeted User DomainRO resulting from a move rather than as an originally or initiallyissued targeted User Domain RO. Although the assisting RI 22 must beassociated with the particular User Domain, the generation and deliveryof the targeted User Domain RO by the assisting RI 22 differs insignificant ways from the generation and delivery of the original orinitial targeted User Domain RO. For instance, the REK is not generatedby the assisting RI 22, but rather is received in encrypted form basedon application of UDK as part of the request from the sourceSCE-conformant DRM Agent, and is not decrypted prior to being encryptedat the RI 22 by applying the sink SCE-conformant DRM Agent's certifiedpublic key.

Consequently, recovery of the REK from the targeted Rights Objectdelivered to the sink SCE-conformant DRM Agent requires knowledge of UDKas well as of the SCE-conformant DRM Agent's private key. Thus, unlikethe case of delivery of the original targeted User Domain RO the sinkSCE-conformant DRM Agent is not required to be a member of the UserDomain at the time of delivery and therefore need not supply a UserDomain Authorization to the RI 22 that represents such membership. Thisaspect parallels the situation of distribution of backwards-compatibleUser Domain ROs, although unlike that case, the RO is targeted to aspecific DRM Agent. The assisting RI not only need not recover the REK,but also, even if rogue, cannot feasibly independently recover REKwithout knowledge of UDK. The assisting RI, even if rogue, cannotconvert the RO to a backwards-compatible User Domain RO usable by v2.xDRM Agents. Furthermore, not every RI associated with the User Domain,even if rogue, can necessarily successfully perform the function ofassisting in move of a targeted User Domain RO corresponding to thatUser Domain, as discussed further herein below.

Typically, the source DRM Agent is presumed to have registered with theRI and to have thus established an RI Context with the RI prior torequesting move of an RO. If the RI Context indicates that the RI hasstored relevant information about the DRM Agent's certificate, it may beunnecessary for the DRM Agent to include its identity certificateinformation in the move targeted User Domain RO request it sends to theRI as source DRM Agent. Similarly, typically, the sink DRM Agent ispresumed to have registered with the RI and to have thus established anRI Context with the RI prior to requesting acquisition of an RO. If theRI Context indicates that the RI has stored relevant information aboutthe DRM Agent's certificate, it may be unnecessary for the DRM Agent toinclude its identity certificate information in the RO acquisitionprotocol request it sends to the RI.

The downstream RI 22 may comprise the RI that initially targeted theUser Domain RO that is to be moved or the targeted User Domain RO mayhave been initially targeted by a different downstream RI 22 or by anLRM 22. In any event, and as discussed in greater detail herein below,the downstream RI 22 is configured to preserve the intent of theoriginal issuer of the RO without reliance on the “transitive trust”model. The “transitive trust” model basically indicates that when a UserDomain RO is moved at different times by different Rls, since the RIcurrently considering assisting in the move has visibility to only thelast RI 22 that moved the RO (or to the original LRM/RI 22 creator ofthe RO), it needs to trust not only that RI for its processing of theRO, but also implicitly trust that RI's judgment in trusting the RI thatmoved it immediately previously (or the original creator RI/LRM), and soon, without necessarily having independently verifiable knowledge of thelist of Rls that the original creator LRM/RI intended to permit toassist in later moving the RO or even of the identity of the originalcreator LRM/RI. Although the original creator LRM/RI can include suchindication in the original RO, any rogue RI along the way cansuccessfully alter such indication unless the precautionary measuresdescribed herein below are taken.

According to an embodiment, the need for an RI that assists in anRI-mediated DRM Agent to DRM Agent move of a User Domain RO toimplicitly trust other Rls that engage in these moves without havingfirst-hand knowledge of their identities is removed. This need isremoved by means of ensuring that any modification of a list of eligibleones of the Rls as intended by the RI or LRM that created the initialUser Domain RO and/or modification of the identity of the RI or LRM thatcreated the initial User Domain RO will result in the RO that istransferred to the sink SCE-conformant DRM Agent as being unusableunless there is collusion between a compromised source DRM Agent and arogue RI, as discussed in greater detail herein below.

Turning now to FIG. 5, there is shown a flow diagram 300 of a method ofmoving a User Domain RO from a source SCE-conformant DRM Agent to arecipient SCE-conformant DRM Agent through operation of a downstream RI22, according to an embodiment of the invention. It should be understoodthat the method 300 depicted in FIG. 5 may include additional steps andthat some of the steps described herein may be removed and/or modifiedwithout departing from a scope of the method 300.

At step 302, a downstream RI 22 receives a request to move a User DomainRO from a source SCE-conformant DRM Agent to a sink SCE-conformant DRMAgent. According to an example, the downstream RI 22 receives therequest from the source SCE-conformant DRM Agent. In addition, therequested User Domain RO to be moved may have been generated asdiscussed above with respect to the method 200 in FIG. 4. Moreover, therequested User Domain RO to be moved may have initially been targetedfor the source SCE-conformant DRM Agent or the source SCE-conformant DRMAgent may have received the User Domain RO directly from anotherSCE-conformant DRM Agent as discussed herein below under Agent to Agentmoves. The requested User Domain RO to be moved may have been targetedfor the source SCE-conformant DRM Agent by the originator RI/LRM 22 ormay have been moved to the source SCE-conformant DRM Agent by anassisting or mediating downstream RI 22.

At step 304, the downstream RI 22 can reliably determine the list of Rlsthat the originating LRM or RI 22 intended to allow to later move the ROand possibly also determine the identity of the originating LRM or RI ifsuch information had been included. Based on this determination, at step306, the RI 22 may make a decision as to whether or not it wants toproceed with processing the request to move the RO. If the RI 22 doesnot trust one or more of the originating LRM or RI 22 or an RI that wasoriginally allowed to move the RO, the method 300 may end as indicatedat step 308.

If the RI trusts the other LRM or RI's or determines that the method 300is to continue at step 306, the RI may receive the identity certificateof the source SCE-conformant DRM Agent as indicated at step 310.Verification of the validity of the request to move the RO is based inpart on accessing the information in or derived from the identitycertificate of the source DRM Agent, including, in particular, thepublic key of the source SCE-conformant DRM Agent and the fact that itis an SCE-conformant DRM Agent based on presence of sceDrmAgent keypurpose. In addition, as indicated at step 312, the downstream RI 22determines whether the source SCE-conformant DRM Agent is valid tosubstantially ensure that the source SCE-conformant DRM Agent hasproperly joined the User Domain. More particularly, for instance, whenthe source SCE-conformant DRM Agent joined the User Domain via the DEA24, the source SCE-conformant DRM Agent received the attributecertificate or User Domain Authorization from the DEA 24. At steps 310and 312, the source SCE-conformant DRM Agent essentially proves to thedownstream RI 22 delivering the User Domain RO that the SCE-conformantAgent is in the User Domain. Alternatively, the RI 22 may have priorknowledge of a still-valid User Domain Authorization for the particularSCE-conformant DRM Agent.

If the source SCE-conformant DRM Agent has not joined the User Domain orhas failed to prove such an association, the downstream RI 22 may returna status indicating error within the response message to theSCE-conformant DRM Agent indicating that the move has been aborted,i.e., that the RI 22 will not generate a targeted User Domain RO for asink SCE-conformant DRM Agent and that the source SCE-conformant DRMAgent can continue to use the rights corresponding to the RO referred toin the request, as indicated at step 308.

At step 314, the downstream RI 22 generates a targeted User Domain ROfor the sink or recipient SCE-conformant DRM Agent using the informationin or derived from the identity certificate of the recipientSCE-conformant DRM Agent. In addition, the downstream RI 22 generatesthe targeted User Domain RO for the recipient SCE-conformant DRM Agentwithout using a User Domain Key, as discussed above with respect to themethod 200 in FIG. 4. In other words, the downstream RI 22 is not givenaccess to the actual REK(s). Instead, the source SCE-conformant DRMAgent must receive the correct value(s) of “PREK” in order for the ROacquisition protocol via the downstream RI 22 to result in the recipientSCE-conformant DRM Agent accessing the correct REK(s) once thatrecipient SCE-conformant DRM Agent is a member of the User Domain. Inparticular, the signature on the request message from the sourceSCE-conformant DRM Agent must have been generated by the entityidentified within the User Domain Authorization that is within the partof the request that is MAC'd (to provide key confirmation), where thisMAC key and the PREK(s) are transmitted within the move request from thesource SCE-conformant DRM Agent in a form that requires access to theRI's private key in order to perform recovery.

As such, when creating the User Domain RO for the recipientSCE-conformant DRM Agent, rather than generating a new REK as done inthe case of initial or original generation of a targeted User Domain ROand using that REK to encrypt (e.g., AES-Wrap) one or more contentencryption keys (CEK) that are used to encrypt or decrypt the content,the downstream RI 22 includes the PREK(s) in the ROs it generates, wherethe RI recovered such PREK(s) from the move request message from thesource SCE-conformant DRM Agent based on knowledge of the RI's privatekey, and includes in the RO the information that the sourceSCE-conformant DRM Agent sent it that presumably corresponds to the(e.g., AES-Wrap) encryption of the CEK(s) under the REK. Thus, unlikethe original or initial generation of a targeted User Domain RO orbackwards-compatible User Domain RO, the RI 22 need not have knowledgeof REK. In other words, the downstream RI 22 generates the targeted UserDomain RO based upon the public key contained in the identitycertificate of the recipient SCE-Conformant DRM Agent.

In any regard, at step 316, the downstream RI 22 communicates thetargeted User Domain RO to the sink or recipient SCE-conformant DRMAgent. The recipient SCE-conformant DRM Agent uses its knowledge of itsprivate key to recover PREK. Since the subsequent recovery of the REKfrom PREK requires knowledge of the UDK, the recipient SCE-conformantDRM Agent must be a member of the User Domain to fully process the RO inorder to enable useful access to the corresponding content, but need notbe in the User Domain at the time the recipient SCE-conformant DRM Agentreceives the targeted User Domain RO nor prove its membership in theUser Domain to the RI in order to receive the RO. The recipientSCE-conformant DRM Agent should verify the inclusion of the ID of the RIin the list of RIs eligible to assist in move of the targeted UserDomain RO. The list of Rls eligible to assist in move, together withpossibly other information such as the identity of the originatingRI/LRM can be in the form of a <moveIndication> element. If PREK hasbeen modified independently of the <moveIndication> element in the RO,recovery of REK will fail. The <moveIndication> element is part of theinformation that is signed by the RI 22, where the signing key isprivate to the RI. Effective modification of PREK requires knowledge ofUDK which is not given to the RI.

As an example formulation of PREK: Let Hash16 denote the first 16 bytesof the SHA-1 hash of the <moveIndication> element. REK is first XORedwith Hash16 and the result is then wrapped with the UDK using theAES-WRAP symmetric wrapping scheme. Let PREK denote the protected REK:

PREK=AES-WRAP(UDK,REK XOR Hash16).

DETAILED DESCRIPTION

In contrast to the method 300 depicted in FIG. 5, there are instanceswhere a direct moving or copying of a User Domain RO from a sourceSCE-conformant DRM Agent to a recipient SCE-conformant DRM Agent isdesired. These instances may occur, for example, when the SCE-conformantDRM Agents do not have access to an RI 22 that is permitted and willingto perform the move or RI-assisted Move is not enabled in the sourceSCE-conformant DRM Agent and/or recipient SCE-conformant DRM Agent. AUser Domain RO that is moved or copied in the method described hereinbelow is assumed to have begun its lifecycle as a targeted (i.e.,<userDomain>-constrained) RO. However, the source SCE-conformant DRMAgent is not necessarily the original or initial recipient of thetargeted RO from a downstream RI/LRM 22. The source SCE-conformant DRMAgent may have alternatively received the RO directly from anotherSCE-conformant DRM Agent or as the result of an RI-assisted move. Priorto onset of the move or copy method described below herein, it may beassumed that the two SCE-conformant DRM Agents have established a SecureAuthenticated Channel (SAC) using standard means based, in particular,on exchange of their identity certificates. The SAC may be used toprotect the integrity and confidentiality of the communications asneeded. In particular, the confidentiality aspect ensures that thetargeting of the RO from the source DRM Agent to the recipient DRM Agentis maintained, in that an eavesdropper even with knowledge of the UDKwill not be able to recover the REK.

The source SCE-conformant DRM Agent must be in the User Domain at thetime the User Domain RO is moved or copied to the SCE-conformant DRMAgent. However, the recipient SCE-conformant DRM Agent need not be amember of the User Domain at the time of the move or copy of the UserDomain RO from the source SCE-conformant DRM Agent.

Turning now to FIG. 6, there is shown a flow diagram 400 of a method ofdirectly moving a User Domain RO from a source SCE-conformant DRM Agentto a recipient SCE-conformant DRM Agent, according to an embodiment ofthe invention. It should be understood that the method 400 depicted inFIG. 6 may include additional steps and that some of the steps describedherein may be removed and/or modified without departing from a scope ofthe method 400.

At step 402, the recipient SCE-conformant DRM Agent requests that a UserDomain RO be moved from a source SCE-conformant DRM Agent. In addition,the recipient SCE-conformant DRM Agent receives an attribute certificateor User Domain Authorization of the source SCE-conformant DRM Agent andthe User Domain RO, as indicated at step 404. Alternatively the sourceSCE-conformant DRM Agent pushes the User Domain RO to the recipientSCE-conformant DRM Agent along with the source SCE-conformant DRMAgent's User Domain Authorization in step 404 without step 402. Even ifknown to the source SCE-conformant DRM Agent, the original targeted UserDomain RO need not necessarily be transmitted in its entirety across thechannel between the source SCE-conformant DRM Agent and recipientSCE-conformant DRM Agent since the information specific to the originalrecipient SCE-conformant DRM Agent is not necessarily of use to therecipient DRM Agent. The protection of sensitive information may be donevia the SAC rather than by encrypting using the recipient SCE-conformantDRM Agent's certified public key and/or using digital signatures.

At step 406, the recipient SCE-conformant DRM Agent determines whetherthe source SCE-conformation DRM Agent is a valid member of the UserDomain. According to an embodiment, the recipient SCE-conformant DRMAgent makes this determination through a comparison of the informationcontained in the data sent along with the part of the User Domain ROthat is communicated and the information that had been embedded in theUser Domain RO by the RI or LRM that initially or last generated theUser Domain RO. More particularly, for instance, the recipientSCE-conformant DRM Agent may compare the fields of the User DomainAuthorization of the RI or LRM that initially or last generated the UserDomain RO against the corresponding fields of the User DomainAuthorization of the source SCE-conformant DRM Agent sent over thechannel from the source SCE-conformant DRM Agent to the recipientSCE-conformant DRM Agent. In addition, the recipient SCE-conformant DRMAgent is not required to be a member of the User Domain to make thisdetermination.

In determining whether the source SCE-conformant DRM Agent is valid atstep 406, the recipient SCE-conformant DRM Agent is configured toperform a number of additional checks. These additional checks mayinclude, for instance, a determination as to whether the sourceSCE-conformant DRM Agent is using an earlier generation of the UserDomain Key than that known to the recipient SCE-conformant DRM Agent, inthe case that the recipient SCE-conformant DRM Agent is already a memberof the User Domain. If the protocol is configured so that the sourceSCE-conformant DRM Agent explicitly sends its User Domain Authorization(within the UserDomainAuthorization field), then the REK can be sentAES-Wrapped under the UDK (as received in step 410 below) without theneed for other means such as herein below for the recipientSCE-conformant DRM Agent to ascertain whether or not the sourceSCE-conformant DRM Agent has knowledge of a legitimately recentgeneration of the UDK.

As an alternative to the source SCE-conformant DRM Agent providing anexplicit User Domain Authorization, according to an embodiment, thischeck may be made by adding (via exclusive-or) a value (namely atruncated one-way hash of the recipient device ID) to REK, such that theincorrect value of REK is recovered by the recipient SCE-conformant DRMAgent if the source Device does not provide the correct sum as input toAES-WRAP under the User Domain Key. Even a recipient SCE-conformant DRMAgent, for instance, Device A, that acquires knowledge (by decryptingusing the security association of the Secure Authenticated Channel) ofAES-WRAP(UDK, REK XOR Trunc(Hash(ID of Device A)), cannot convert thisto AES-WRAP(UDK, REK XOR Trunc(Hash(ID of Device B)) for some otherDevice B not equal to Device A without first acquiring knowledge of UDKby joining the domain. If this configuration is used, this value is sentin place of AES-WRAP(UDK, REK) as described above during step 410.

If any of the checks indicates that the source SCE-conformant DRM Agentis invalid or may otherwise be unauthorized to perform the move or copyof the User Domain RO, the recipient SCE-conformant DRM Agent may endthe method 400 as indicated at step 408.

If, however, the recipient SCE-conformant DRM Agent determines that theinformation the source SCE-conformant DRM Agent had sent is valid atstep 406, it can respond to this effect and accept receipt in step 410of the encrypted REK value. Once the encrypted REK value has been sentby the source SCE-conformant DRM Agent, the source SCE-conformant DRMAgent cannot necessarily safely abort the move. Whether or not therecipient SCE-conformant DRM Agent acknowledges successful orunsuccessful receipt of the encrypted REK value, there is a possibilitythat this acknowledgement is not received intact by the sourceSCE-conformant DRM Agent. A copy operation can be done in two passeseven if move is done in four passes, since recovery from communicationsfailure may be less of an issue for copy. Thus the encrypted REK can besent in the first pass, where if the acknowledgement from the recipientDRM Agent indicates failure but passes the SAC integrity check, the copyoperation can be safely aborted.

Some or all of the operations set forth in the figures may be containedas a utility, program, or subprogram, in any desired computer readablestorage medium. In addition, the operations may be embodied by computerprograms, which can exist in a variety of forms both active andinactive. For example, they may exist as software program(s) comprisedof program instructions in source code, object code, executable code orother formats. Any of the above may be embodied on a computer readablestorage medium, which include storage devices.

Exemplary computer readable storage media include conventional computersystem RAM, ROM, EPROM, EEPROM, and magnetic or optical disks or tapes.Concrete examples of the foregoing include distribution of the programson a CD ROM or via Internet download. It is therefore to be understoodthat any electronic device capable of executing the above-describedfunctions may perform those functions enumerated above.

FIG. 7 illustrates a block diagram of a computing apparatus 700configured to implement or execute one or more of the processes depictedin FIGS. 3-6, according to an embodiment. It should be understood thatthe illustration of the computing apparatus 700 is a generalizedillustration and that the computing apparatus 700 may include additionalcomponents and that some of the components described may be removedand/or modified without departing from a scope of the computingapparatus 700.

The computing apparatus 700 includes a processor 702 that may implementor execute some or all of the steps described in one or more of theprocesses depicted in FIGS. 3-6. Commands and data from the processor702 are communicated over a communication bus 704. The computingapparatus 700 also includes a main memory 706, such as a random accessmemory (RAM), where the program code for the processor 702, may beexecuted during runtime, and a secondary memory 708. The secondarymemory 708 includes, for example, one or more hard disk drives 710and/or a removable storage drive 712, representing a floppy diskettedrive, a magnetic tape drive, a compact disk drive, etc., where a copyof the program code for one or more of the processes depicted in FIGS.2-6 may be stored.

The removable storage drive 710 reads from and/or writes to a removablestorage unit 714 in a well-known manner. User input and output devicesmay include a keyboard 716, a mouse 718, and a display 720. A displayadaptor 722 may interface with the communication bus 704 and the display720 and may receive display data from the processor 702 and convert thedisplay data into display commands for the display 720. In addition, theprocessor(s) 702 may communicate over a network, for instance, theInternet, LAN, etc., through a network adaptor 724.

It will be apparent to one of ordinary skill in the art that other knownelectronic components may be added or substituted in the computingapparatus 700. It should also be apparent that one or more of thecomponents depicted in FIG. 7 may be optional (for instance, user inputdevices, secondary memory, etc.).

While the embodiments have been described with reference to examples,those skilled in the art will be able to make various modifications tothe described embodiments without departing from the true spirit andscope. The terms and descriptions used herein are set forth by way ofillustration only and are not meant as limitations. In particular,although the methods have been described by examples, steps of themethods may be performed in different orders than illustrated orsimultaneously. Those skilled in the art will recognize that these andother variations are possible within the spirit and scope as defined inthe following claims and their equivalents.

1. A method of moving a user domain rights object (RO) from a sourcesecure content exchange (SCE) conformant digital rights management (DRM)agent to a recipient SCE-conformant DRM agent through operation of arights issuer (RI), said method comprising: receiving a request to movea user domain RO from the source SCE-conformant DRM Agent to therecipient SCE-conformant DRM Agent; receiving an identity certificate ofthe source SCE-conformant DRM agent; determining whether the sourceSCE-conformant DRM agent is valid; generating a targeted user domain ROfor the recipient SCE-conformant DRM agent using at least one ofinformation contained in and derived from the identity certificate ofthe source SCE-conformant DRM agent; and communicating the targeted userdomain RO to the recipient SCE-conformant DRM agent.
 2. The methodaccording to claim 1, further comprising: identifying a list of rightsissuers (RIs) that an originating local rights manager or RI intended toallow to later move the user domain RO; determining whether the list ofRIs contains an untrusted RI; and aborting the move in response to thelist of RIs containing an untrusted RI.
 3. The method according to claim1, wherein generating the targeted user domain RO for the recipientSCE-conformant DRM agent further comprises generating the targeted userdomain RO for the recipient SCE-conformant DRM without use by the RI ofa user domain key.
 4. The method according to claim 1, whereindetermining whether the source SCE-conformant DRM agent is valid furthercomprises accessing information pertaining to a public key of the sourceSCE-conformant DRM agent contained in or derived from the identitycertificate of the source SCE-conformant DRM agent.
 5. The methodaccording to claim 1, further comprising: aborting the move in responseto the source SCE-conformant DRM agent being invalid.
 6. The methodaccording to claim 1, wherein generating the targeted user domain RO forthe recipient SCE-conformant DRM agent further comprises using theinformation provided to the RI by the source SCE-conformant DRM agentthat includes PREK(s) and the encryption of one or more contentencryption keys (CEK(s)) under the rights object encryption key (REK)corresponding to a PREK, wherein the RI includes the PREK(s) in the ROsthat the RI generates, wherein the RI is configured to recover thePREK(s) from a move request message from the source SCE-conformant DRMagent based on knowledge of a private key of the RI, and wherein theuser domain RO includes information received from the sourceSCE-conformant DRM Agent that corresponds to the encryption of theCEK(s) under the REK.
 7. The method according to claim 1, whereingenerating the targeted user domain RO further comprises generating thetargeted user domain RO based upon a public key contained in an identitycertificate of the recipient SCE-conformant DRM Agent.
 8. The methodaccording to claim 7, wherein the recipient SCE-conformant DRM agentuses its knowledge of the private key of the recipient SCE-conformantDRM agent to recover a PREK.
 9. The method according to claim 1 whereinthe recipient SCE-conformant DRM agent is not a member of user domainwhen the targeted User Domain RO is communicated to the recipientSCE-conformant DRM agent.
 10. The method according to claim 9, whereinthe recipient SCE-conformant DRM agent uses its knowledge of a userdomain key to decrypt a recovered PREK to recover an REK.
 11. A computerprogram product comprising a non-transitory computer-readable storagemedium storing executable code for moving a user domain rights object(RO) from a source secure content exchange (SCE) conformant digitalrights management (DRM) agent to a recipient SCE-conformant DRM agentthrough operation of a rights issuer (RI), the code when executed by atleast one processor causes the processor to perform steps comprising:receiving a request to move a user domain RO from the sourceSCE-conformant DRM Agent to the recipient SCE-conformant DRM Agent;receiving an identity certificate of the source SCE-conformant DRMagent; determining whether the source SCE-conformant DRM agent is valid;generating a targeted user domain RO for the recipient SCE-conformantDRM agent using at least one of information contained in and derivedfrom the identity certificate of the source SCE-conformant DRM agent;and communicating the targeted user domain RO to the recipientSCE-conformant DRM agent.
 12. The computer program product according toclaim 11, wherein the code when executed by the processor further causesthe processor to perform steps comprising: identifying a list of rightsissuers (RIs) that an originating local rights manager or RI intended toallow to later move the user domain RO; determining whether the list ofRIs contains an untrusted RI; and aborting the move in response to thelist of RIs containing an untrusted RI.
 13. The computer program productaccording to claim 11, wherein generating the targeted user domain ROfor the recipient SCE-conformant DRM agent further comprises generatingthe targeted user domain RO for the recipient SCE-conformant DRM withoutuse by the RI of a user domain key.
 14. The computer program productaccording to claim 11, wherein determining whether the sourceSCE-conformant DRM agent is valid further comprises accessinginformation pertaining to a public key of the source SCE-conformant DRMagent contained in or derived from the identity certificate of thesource SCE-conformant DRM agent.
 15. The computer program productaccording to claim 11, wherein the code when executed by the processorfurther causes the processor to perform steps comprising: aborting themove in response to the source SCE-conformant DRM agent being invalid.16. The computer program product according to claim 11, whereingenerating the targeted user domain RO for the recipient SCE-conformantDRM agent further comprises using the information provided to the RI bythe source SCE-conformant DRM agent that includes PREK(s) and theencryption of one or more content encryption keys (CEK(s)) under therights object encryption key (REK) corresponding to a PREK, wherein theRI includes the PREK(s) in the ROs that the RI generates, wherein the RIis configured to recover the PREK(s) from a move request message fromthe source SCE-conformant DRM agent based on knowledge of a private keyof the RI, and wherein the user domain RO includes information receivedfrom the source SCE-conformant DRM Agent that corresponds to theencryption of the CEK(s) under the REK.
 17. A system for moving a userdomain rights object (RO) from a source secure content exchange (SCE)conformant digital rights management (DRM) agent to a recipientSCE-conformant DRM agent through operation of a rights issuer (RI),system comprising: at least one processor; and one or morenon-transitory computer-readable storage media storing executable code,the code when executed by the processor causes the processor to performsteps comprising: receiving a request to move a user domain RO from thesource SCE-conformant DRM Agent to the recipient SCE-conformant DRMAgent; receiving an identity certificate of the source SCE-conformantDRM agent; determining whether the source SCE-conformant DRM agent isvalid; generating a targeted user domain RO for the recipientSCE-conformant DRM agent using at least one of information contained inand derived from the identity certificate of the source SCE-conformantDRM agent; and communicating the targeted user domain RO to therecipient SCE-conformant DRM agent.
 18. The computer system according toclaim 17, wherein the code when executed by the processor further causesthe processor to perform steps comprising: identifying a list of rightsissuers (RIs) that an originating local rights manager or RI intended toallow to later move the user domain RO; determining whether the list ofRIs contains an untrusted RI; and aborting the move in response to thelist of RIs containing an untrusted RI.
 19. The computer systemaccording to claim 17, wherein generating the targeted user domain ROfor the recipient SCE-conformant DRM agent further comprises generatingthe targeted user domain RO for the recipient SCE-conformant DRM withoutuse by the RI of a user domain key.
 20. The computer system according toclaim 17, wherein determining whether the source SCE-conformant DRMagent is valid further comprises accessing information pertaining to apublic key of the source SCE-conformant DRM agent contained in orderived from the identity certificate of the source SCE-conformant DRMagent.